(1) Field of the Invention
The present invention relates to elastic polyester fibers and stretchable fiber articles containing the elastic polyester fibers. More particularly, the present invention relates to elastic polyester fibers which have been produced in a stable condition without occurrence of cohesion of fibers to each other during the fiber production and without generation of static electricity due to contact and abrasion of the fibers with guides and rolls, and which have an excellent smoothness, durable hydrophilicity and stable suspension in water and exhibit a high processability through carding machine and spinning machine, and stretchable fiber articles, for example, nonwoven, woven and knitted fabrics and packing fiber masses comprising the elastic polyester fibers.
(2) Description of Related Art
It is known that conventional elastic fibers made from a polyester elastomer are mostly cohered to each other during fiber-forming and taking up procedures and thus are unsuitable for the use in which the elastic fibers are opened or suspended in water, and the resultant fiber article have many defects derived from the cohered and bundled fibers. Therefore, the resultant fiber article exhibits an unsatisfactory formation, a reduced mechanical strength, elongation and elasticity and a decreased uniformity in the above-mentioned properties.
Also, when used in dry-laid nonwoven fabrics, packing fiber masses or spun yarns, the conventional elastic polyester fibers exhibit a poor processability in carding and spinning procedures due to the high elasticity of the fibers and a high friction between the fibers and guides or rolls, and thus the resultant final product exhibits an undesirable cohesive hand.
Further, the conventional elastic polyester fibers are disadvantageous in that when a plurality of packages of the fibers are stored in accumulated condition, for example, in a storehouse or truck without air-conditioning in summer season, the fibers are mostly cohered to each other.
Several attempts have been made to solve the above-mentioned problems. For example, Japanese Unexamined Patent Publication No. 5-302,255 discloses a core-in-sheath type elastic polyester composite fiber in which a core formed from a polyester elastomer is surrounded by a sheath made from another polyester elastomer containing a reduced amount of soft segments and having a decreased cohesive property. However, when the sheath polyester elastomer has a satisfactorily reduced cohesive property, the resultant core-in-sheath composite fiber exhibits an unsatisfactory elasticity.
Also, Japanese Unexamined Patent Publication No. 57-82,553 and No. 3-8,855 disclose a process for producing elastic filaments from an elastomer, while preventing undesirable cohesion of spun individual filaments with each other by carrying out the filament-forming (spinning) procedure with a reduced number of the individual filaments of 30 or less. This process is, however, unsatisfactory in that the resultant individual filament bundle exhibit an insufficient capability of being opened and the producibility of the elastic filaments is low. Also, when the spun filaments are stored or transported in a raised temperature condition, for example, in the summer season, it is not possible to fully prevent the cohesion of the filaments with each other.
Further, Japanese Unexamined Patent Publication No. 5-140,853 discloses a method of preventing a cohesion phenomenon of elastomer fibers by adding 1 to 10% by weight of a polyolefin and 1 to 8% by weight of fine inorganic particles to the elastomer fibers. However, in this method it is difficult to prevent the cohesion of elastomer fibers with each other, during a fiber-spinning procedure, to a satisfactory extent.
Still further, Japanese Examined Patent Publications No. 47-11,280 and No. 60-56,802 disclose synthetic fibers containing a sulfonic acid metal salt compound mixed in a synthetic resin. In these synthetic fibers, the sulfonic acid metal salt compound is used for the purpose of imparting an antistatic property to the synthetic fibers. In accordance with the research of the inventors of the present invention, when the sulfonic acid metal salt compound alone is incorporated into a polyester elastomer, the resultant polyester elastomer article does not exhibit a sufficient anti-cohesion property.